687270651
TSG-C
SWG 1.3
TITLE: Jitter Parameter Specification for IS-707-B QoS BLOB Extensions
SOURCE:
Lucent Technologies
D. N. Knisely
ABSTRACT:
It is proposed that jitter parameters be added to the IS-707-B QoS BLOB (per requests from
Sprint PCS and Qualcomm), and that those parameters be expressed in terms of parameters
that model the statistical distribution of the delay, where delay is measured from the top of
the transmitting RLP entity to the top of the receiving RLP entity. Jitter control operation
can be successfully controlled using three parameters of the traffic delivery: the long-term
playout rate at the receiver, the mean delay, and the standard deviation around the mean
delay.
RECOMMENDATION:
Discuss and adopt as the approach for the inclusion of jitter-related parameters in the IS707-B QoS BLOB.
Lucent Technologies grants a free, irrevocable license to 3GPP2 and its Organizational Partners
to incorporate text or other copyrightable material contained in the contribution and any
modifications thereof in the creation of 3GPP2 publications; to copyright and sell in
Organizational Partner's name any Organizational Partner's standards publication even though it
may include all or portions of this contribution; and at the Organizational Partner's sole discretion
to permit others to reproduce in whole or in part such contribution or the resulting Organizational
Partner's standards publication. Lucent Technologies is also willing to grant licenses under such
contributor copyrights to third parties on reasonable, non-discriminatory terms and conditions for
purpose of practicing an Organizational Partner’s standard which incorporates this contribution.
This document has been prepared by Lucent Technologies to assist the development of
specifications by 3GPP2. It is proposed to the Committee as a basis for discussion and is not to
be construed as a binding proposal on Lucent Technologies. Lucent Technologies specifically
reserves the right to amend or modify the material contained herein and to any intellectual
property of Lucent Technologies other than provided in the copyright statement above.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
Overview
This contribution proposes to define SO33 QoS BLOB parameters defining “jitter” such
that the negotiated parameters define a statistical distribution of the transmission delay
from the top of the transmitting RLP entity to the top of the receiving RLP entity. The
characteristics of this distribution are as follows:
1. The negotiated distribution parameters define a “contract” by the transmitting and
receiving RLP entities (and the and the supporting lower layers) to provide for the
delivery of RLP SDU octets from the transmitting upper layer entities to the
receiving upper layer entities according to a long term statistical distribution
defined by the parameters.
2. The BS selects operating parameters for RLP (e.g., number of NAK rounds,
number of NAKs/round) and the lower layers (e.g., the type and number of
Physical Channels, the operating parameters for those channels such as ARQ,
scheduling policy parameters, etc.) such that the agreed upon distribution of delay
is satisfied in the long term.
3. The distribution of RLP to RLP delay is specified by the following parameters
(see Figure 1):
Parameter
Definition
The long-term average data delivery rate (from
r
the service option to the upper layers).1
The mean delay of data delivery (from the top of
m
the transmitting RLP to the top of the receiving
RLP).
The standard deviation around the mean m of data
s
delivery (from the top of the transmitting RLP to
the top of the receiving RLP).
4. The receiver (e.g., the MS for a forward transmission jitter parameter
specification) must provide for sufficient jitter management capabilities (e.g.,
dejittering buffer space, need to delay delivery of the initial octets of the data
stream to the upper layers, etc.) as necessary to provide for a reasonable statistical
likelihood that the upper layer entities QoS needs will be satisfied.
5. Given the contractual commitment made by the BS to satisfy the delay
distribution, the receiver (MS or BS) can determine the need for resources (e.g.,
dejitter buffer size) and make all necessary tradeoffs vs. risk of failing to meet the
upper layer entity’s QoS needs. However, the risk can be determined accurately
based on the statistical commitments of the delay distribution contract. The
specific manner for how these capabilities are provided in the receiver are not
specified by standards.
1
Note that the currently defined data rate in the QoS BLOB may be redefined to determine r if the other
jitter parameters are included in the BLOB.
2
Safe Region
(as Determined
by Receiver)
Does Not
Happen
(Dropped)
Overrun
Risk
Region
Underrun
Risk
Region
Underrun
Region
Overrun
Region
p(delayRLP = t)
t
t=0
m-s
m-n1*s
MAX_
m+s
DELAY
mean =
m
m+n2*s
n1 and n2 Selected by Receiver, e.g.,
n1 = n2 = 1 => ~68% Coverage of Safe Region
n1 = n2 = 2 => ~95% Coverage of Safe Region
n1 = n2 = 3 => ~99% Coverage of Safe Region
Negotiated Parameters
(Proposed by MS and Set by BS):
r = Longterm Average Data Delivery Rate
m = Mean Delay of Data Delivery (top of
Transmitter RLP to top of Receiver RLP)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
s = Standard Deviation Around Mean m of Data
Delivery (top of Transmitter RLP to top of Receiver
RLP)
Figure 1. Parameters Defining the Distribution of RLP-RLP Delay
Negotiation of Parameters
The following steps are proposed for the negotiation of jitter-related QoS BLOB
parameters:
1. The MS may optionally propose values for (ru, mu, su) for the jitter control of the
uplink RLP stream.
2. The MS may optionally propose values for (rd, md, sd) for the jitter control of the
downlink RLP stream.
3. The BS responds to the proposed uplink and downlink proposals with the actual
values for (ru, mu, su) and (rd, md, sd) that will be used for this service instance.
There are no constraints on the values that may be selected by the BS; however,
the BS may take the proposed values from the MS into consideration in
determining the actual values. The MS proposed values may be indicative of
application requirements known on the MS.
4. If the BS omits either triplet, the interpretation at the MS is that no jitter control
will be provided by the BS for this service instance.
5. The BS may also include either the uplink or downlink parameters even if no
corresponding jitter-related parameters were proposed by the MS.
6. The MS may accept or reject the jitter control parameters selected by the BS.
3
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
Benefits
There are several benefits to this approach for negotiating jitter in the QoS BLOB:
1. The method precisely characterizes (and constrains) the acceptable delay
characteristics for the peer RLP entities and the supporting lower layers.
2. The method is extremely implement independent for both the transmitter and the
receiver (RLP and lower layers). In particular, there are no specific
implementation details about MS dejittering implementations that would be
specified in the standard. For example, this method avoids contentious issues
regarding the mandatory specification for MS buffer sizes.
3. Despite the lack of precise implementation constraints in the standard, the
implementations can be extremely robust.
4. The parameters are meaningful in understanding application delay characteristics.
The parameters can be easily mapped to/from parameters that the higher layers
(e.g., applications) specify or “understand” (e.g., via application APIs).
5. The parameters can be easily mapped to/from the operational parameters that are
used on the transmitter and receiver (e.g., to determine required dejitter buffer
size).
Recommendations
Adopt this parametric approach (r, m, s) and negotiation procedures for specifying jitterrelated parameters in the IS-707-B QoS BLOB.
4
1
2
3
4
5
6
7
8
9
10
Simulation Results
A simple model was constructed to simulate an over-the-air RLP to RLP delivery with a
normally distributed delay (mean delay = m; standard deviation s). Data was played out
of the receiver’s dejitter buffer at a constant rate r. The dejitter buffer status was
monitored to determine the feasibility of designing a simple, stable dejittering mechanism
based solely on the modeling of the delivery distribution parameters. No particular
preloading procedure was simulated; the receiver can determine the best preloading
strategy based on empirical results, knowledge of application requirements, etc.
Simulation Parameters:
Parameter
Rate
Mean Delay
Standard Deviation for Delay
PDU Size
Instantaneous Rate
Long-term Average PDU Rate
Symbol
r
m
s
pdu_size
Value
32
5
1
768
614.4
41.66666667
pdu_rate
Units
Kbps
s
s
bits/packet
Kbps
pkts/second
11
Buffer Status and Playout (m = 5; s = 1)
2000
Cumulative Delivered Octets
140000
1500
120000
1000
100000
500
80000
0
60000
-500
40000
-1000
20000
39
37.6
36.2
34.7
33.3
31.9
30.5
29.1
27.7
26.2
24.8
22
23.4
20.6
19.2
17.7
16.3
14.9
13.5
12.1
10.7
9.25
7.83
5
-1500
6.42
0
Dejitter Buffer Status (Octets); No Preloading
160000
Time (Seconds)
12
13
Figure 2. Simulation of Normally Distributed Data Delivery and Dejitter Buffer Status
14
5
Delivered Octets
Transported Octets
Dejitter Buffer Status